This invention relates to an abrasion resisting flexible joint pipe.
Such kind of joint pipe has heretofore been used for flexibly connecting opposed end tubes made of rigid material such as metal and the like and adapted to transfer mud or sand removed as by dredging.
As shown in FIG. 1, a prior art flexible joint pipe comprises an elastic rubber body whose length l, that is, a distance between opposed end tubes 1, 1', is made considerably long for the purpose of easily deforming the elastic rubber body. As a result, if the elastic rubber body is bent as shown in FIG. 2, a bending angle .theta. formed by the intersection of two center axes of the opposed end tubes 1, 1' becomes large and a sharp body such as crushed stone and the like contained in fluid to be transferred collides with the cylindrical inner rubber surface 2 of the elastic rubber body in a direction inclined from the cylindrical inner rubber surface 2 by an angle .alpha. which is approximately one half the bending angle .theta., thereby considerably wearing away the elastic rubber body by friction. In FIG. 1, reference numeral 3 designates a cylindrical reinforcing layer composed of at least two rubberized cord fabrics arranged so that parallel rubberized cords 3', 3" (FIG. 7) run in opposite directions, making an angle .beta. with a common center axis x--x of the opposed end tubes 1, 1', 4 a wire firmly binding each end of the reinforcing layer 3 about the opposed end tubes 1, 1', and 5 a cylindrical outer rubber surface of the elastic rubber body. The inner and outer rubber surfaces 2 and 5 are made integral with each other to form the elastic rubber body with the reinforcing layer 3 embedded therein.
Experimental tests have yielded the result that the amount of abrasion becomes maximum when the collision angle .alpha. arrives at 30.degree. as shown in FIG. 3 which graphically illustrates the relation between the collision angle .alpha. and the amount of abrasion of the flexible joint pipe.